The present invention relates generally to a structure for mounting a gear, a roller, or another rotary member and more particularly to an image forming apparatus, such as a printer or a facsimile machine, which performs a process for forming an image on a sheet material and employs this improved structure for mounting a gear, a roller, or another rotary member.
A typical example of an image forming apparatus based on the prior art is disclosed in Japanese Patent Application Laid Open No. 222270-1989 (Heisei 1). The mounting structure for a gear in the motive power transmitting mechanism for this apparatus is shown in FIG. 15, and is a structure formed with a first supporting shaft 502, which supports a gear 501, being fixed in a frame 503, or formed with a gear mounted on each of both the ends of a second supporting shaft 505 inserted into a shaft bearing 504.
An additional example of a prior art mounting structure, as shown in FIG. 16, 17 and 18, including a structure for mounting a component part by an application of a burring shaping process, is found in the structure disclosed in Japanese Patent Application Laid Open No. 34531-1989 (Showa 64). This structure is formed by forming a burring part 511 on a metal plate 510, mounting a rotary member or a sliding member 512 on this burring part 511, as shown in FIG. 16, and then bending a top end 513 of burring part 511 as shown in FIGS. 17 and 18, thereby preventing the rotary member or sliding member 513 from falling off. However, these structures have a number of significant limitations.
The environment surrounding computers in the more recent years is marked by a progressive downsizing of the size of computers, compact notebook type computers rising to a position of far greater importance than ever before. Along with this tendency, the market for personal computers has been enlarged to such an extent that there are now more intensified demands for the appearance of more compact external peripheral equipment, such as printers and facsimile machines. These peripherals must be offered for sale at lower prices, and must be smaller for use with compact-sized computers. Together, these components must be capable of being arranged on an individual person's desk leaving free work space still available. The prior art mentioned above cannot respond to such demand.
The structure for mounting a gear as disclosed in Japanese Patent Application Laid Open No. 222270-1989 (Heisei 1), described above, is formed of a large number of component parts and is complicated, so that it is difficult to achieve a reduction in the size of this apparatus or to realize a reduction in its cost. On the other hand, the structure disclosed in Japanese Patent Application Laid Open No. 34531-1989 (Show 64) is formed of a fewer number of component parts and has a relatively simple structure, so that it is considered to be relatively easy to achieve a reduction in the size of the apparatus and to achieve a reduction in its cost. Yet, this structure requires a processing operation for bending the top end portion 513 of the burring part. If this bending process is not performed with high accuracy, a gap w formed during the bending of each part, shown in FIG. 17, will not be uniform for all parts. Thus, it will not always be possible to attain stability during rotation of the rotary member or sliding member 512. Either the part will be too loose, which will result in vibrations during rotation, or the part will be too tight, which will result in a loss of torque due to friction.
Accordingly, it would be advantageous to provide a structure for mounting a rotary member which achieves a reduction in size of the apparatus and a reduction in its cost, which attains stability during rotation of the rotary member, and which offers an image forming apparatus using this improved structure for mounting a rotary member.